1. Field of the Invention
The present invention is directed to computer systems; and more particularly, it is directed to the simulation of brushes for deposition of paint or ink onto a virtual canvas using computer systems.
2. Description of the Related Art
Digital image editing is the process of creating and/or modifying digital images using a computer system. Using specialized software programs, users may manipulate and transform images in a variety of ways. These digital image editors may include programs of differing complexity such as limited-purpose programs associated with acquisition devices (e.g., digital cameras and scanners with bundled or built-in programs for managing brightness and contrast); limited editors suitable for relatively simple operations such as rotating and cropping images; and professional-grade programs with large and complex feature sets.
Digital images may include raster graphics, vector graphics, or a combination thereof. Raster graphics data (also referred to herein as bitmaps) may be stored and manipulated as a grid of individual picture elements called pixels. A bitmap may be characterized by its width and height in pixels and also by the number of bits per pixel. Commonly, a color bitmap defined in the RGB (red, green blue) color space may comprise between one and eight bits per pixel for each of the red, green, and blue channels. An alpha channel may be used to store additional data such as per-pixel transparency values. Vector graphics data may be stored and manipulated as one or more geometric objects built with geometric primitives. The geometric primitives (e.g., points, lines, paths, polygons, Bezier curves, and text characters) may be based upon mathematical equations to represent parts of vector graphics data in digital images. The geometric objects may typically be located in two-dimensional or three-dimensional space. A three-dimensional object may be represented in two-dimensional space for the purposes of displaying or editing the object.
An operation often provided by a digital image editor is the use of a virtual “paintbrush” (also referred to herein as a brush) to modify a digital image by depositing virtual paint or virtual ink. Various prior approaches have attempted to model a real-world brush and its behavior in the context of such an operation. For example, a two-dimensional (2D) raster image may be created to represent the shape of the brush as it contacts the canvas, and the 2D image may be stamped repeatedly along the input path. In another approach, a vector representation of the brush tip has been used instead of a 2D raster image. However, undesirable artifacts may be created by these approaches, particularly when the stamping rate is insufficiently high.